The present invention relates to a compound oxide possessing especially excellent oxygen absorbing and desorbing capability and utilizable for a catalyst for purifying exhaust gas and for ceramics as well as a method for preparing same.
From the past, a cerium oxide is used in large quantities for catalysts for purifying exhaust gas and for ceramics, and in the filed of catalysts, for example, for enhancing the purification rate of exhaust gas components such as hydrocarbons, carbon monoxide and NO.sub.x taking advantage of the characteristic property of cerium oxide capable of absorbing oxygen in an oxidative atmosphere and desorbing oxygen in a reducing atmosphere, while in the filed of ceramics, for use in electroconductive ceramics such as solid electrolytes taking advantage of the aforesaid characteristic property of cerium oxide. Such cerium oxide heretofore known is usually prepared, for example, by adding oxalic acid or ammonium bicarbonate to a solution of nitrate or hydrochloride of cerium, filtering and washing the resultant precipitate and drying followed by baking it.
However, a conventional oxide composed predominantly of cerium oxide prepared according to the above method, though it possesses oxygen absorbing and desorbing capability, fails to absorb or desorb oxygen sufficiently at a temperature of 400.degree.-700.degree. C. and brings about a drawback such that it is reduced in specific surface area after heating at a higher temperature and is thus lowered in performance.